Medaka Breeding Guide — From Egg Collection to Raising Fry

Medaka breeding offers an accessibility that even beginners can enjoy. With the basics mastered, you can tackle breeding beautiful improved varieties.

Medaka Breeding Requirements

Three conditions are needed for medaka to breed:

• Water temperature: 20C or above (25-28C is optimal)
• Daylight hours: 13 or more hours of light
• Nutrition: Sufficient feeding to build stamina

Under natural conditions, breeding season runs April through October, but year-round breeding is possible with a heater and lighting.

Making Spawning Beds

Commercial Spawning Beds Floating medaka spawning beds are convenient. Place 2-3 per tank.

DIY Method 1. Cut 100-yen shop tulle fabric to 10cm width 2. Bundle and secure with a cable tie 3. Attach a foam float

Egg Collection Methods

• Daily checks: Medaka spawn every morning; check beds in the morning
• Egg recovery: Transfer the entire spawning bed to a separate container, or gently remove eggs by hand
• Eggs are surprisingly tough: Fertilized eggs are transparent and won't crush when touched

Egg Management

1. Isolate in separate container -- Place in a food container or plastic case with tap water (containing chlorine)
2. Chlorine's benefit -- Chlorine in tap water helps prevent fungus
3. Temperature management -- About 10 days at 25C, about 7 days at 28C to hatch
4. Daily water changes -- Change water daily with tap water
5. Remove unfertilized eggs -- Remove eggs that turn white and cloudy

Fry (Needle Fry) Rearing

Newly hatched medaka fry are called "needle fry" (hari-ko).

• First 2-3 days: No feeding needed (growth from yolk sac)
• Initial feeding: Paramecium, PSB (photosynthetic bacteria), powdered fry food
• Green water: Raising in green water significantly increases needle fry survival rates
• After 2 weeks: Newly hatched brine shrimp, fine prepared food
• After 1 month: Regular medaka food (fine granule)

Variety Fixation

Key points when breeding improved varieties:

• Same-variety pairs: Don't mix different varieties
• Selection: Choose offspring showing parental traits as next-generation parents
• F2 and beyond matters: F1 (first generation) may not express desired traits
• Manage culled fish: Keep rejected specimens in separate containers

Breeding Notes

• Avoid overcrowding: Target 1 fish per liter
• Separate parents and fry: Parents will eat fry
• Watch high temperatures: Above 35C negatively affects egg development
• Inbreeding: Introduce different bloodlines after 3-4 generations

Benefits of Buying on Buri-Choku

On Buri-Choku, you can purchase directly from improved medaka specialist breeders. Bloodline information and fixation rates can be verified, with abundant pair sales available for breeding.